On October 13 in 1819, 23-year-old John Keats (books by this author) composed what's considered to be one of the most beautiful love letters ever written:

My dearest Girl,

This moment I have set myself to copy some verses out fair. I cannot proceed with any degree of content. I must write you a line or two and see if that will assist in dismissing you from my Mind for ever so short a time. Upon my Soul I can think of nothing else — The time is passed when I had power to advise and warn you again[s]t the unpromising morning of my Life — My love has made me selfish. I cannot exist without you — I am forgetful of every thing but seeing you again — my Life seems to stop there — I see no further. You have absorb'd me. I have a sensation at the present moment as though I was dissolving — I should be exquisitely miserable without the hope of soon seeing you. I should be afraid to separate myself far from you. My sweet Fanny, will your heart never change? My love, will it? I have no limit now to my love — Your note came in just here — I cannot be happier away from you — 'T is richer than an Argosy of Pearles. Do not threat me even in jest. I have been astonished that Men could die Martyrs for religion — I have shudder'd at it — I shudder no more — I could be martyr'd for my Religion — Love is my religion — I could die for that — I could die for you. My Creed is Love and you are its only tenet — You have ravish'd me away by a Power I cannot resist: and yet I could resist till I saw you; and even since I have seen you I have endeavoured often "to reason against the reasons of my Love." I can do that no more — the pain would be too great — My Love is selfish — I cannot breathe without you.
Yours for ever
John Keats

"My dearest Girl" is Fanny Brawne;  the two had met the previous autumn at the house of mutual family friends. In the spring, he and she became next-door neighbors, saw each other all the time, and fell in love. He dashed off playful sonnets to her in the midst of working on his serious verse.

They secretly got engaged, but Keats could not afford to marry her. Though his passion lay with poetry — and publishers were interested in his work — he decided he would write a play in order to make a lot of money quickly. He started working on a historical play about the true love of Elizabeth I.

But in February, months after he'd written "My dearest girl … I cannot breathe without you," John Keats began coughing up blood. He had contracted tuberculosis, the disease that had recently killed his brother Tom. On a blustery February night, Keats had gone to visit friends in the city and returned late, riding outside the stagecoach and without a jacket. He was feverish and his friend took him up to bed, where Keats coughed blood onto the bed sheets, looked at it with a candle and said, "I know the color of that blood; it is arterial blood. I cannot be deceived in that color. That drop of blood is my death warrant. I must die."

He had a second hemorrhage and grew increasingly weak. He had worrisome, inexplicable heart palpitations, which one doctor attributed to hysteria. Keats wrote to Fanny Brawne to tell her that she was free to break off their engagement since he would likely not survive. She would do no such thing, she told him — and he was hugely relieved. But his friends tried to keep the two apart, lest passion make the young poet feel ill.

In June 1820, a book of his poems had been released, and it met with great critical reception and good sales. This news buoyed his spirits, but his illness continued to worsen. Some suggested that he should travel to warm, sunny Italy to get better, and he began making plans to do so.

Then one night, Keats was handed a letter written to him by Fanny, which someone else had inadvertently opened. For some reason this threw him into the depths of despair: He sobbed for hours and set off walking in the night, alone, crying, coughing, consumptive, to where Fanny's family had moved — a mile away. He showed up looking weak and gaunt, and Fanny's mother — one of the few people who knew of their engagement — defied convention and let the young man stay with them that night. He would actually continue staying there for an entire month, and considered it the happiest time of his life.

But soon after that, his travel plans for Italy were complete. A friend took him to Rome, where Keats died at the age of 25. He was buried in the Cemetery for Non-Catholic Foreigners in a plot next to the pyramid. He asked to be buried with an unread letter from Fanny and a lock of her hair. And he asked that his epitaph read, "Here lies one whose name was writ in water."

And he wrote her: "My Mind has been the most discontented and restless one that ever was put into a body too small for it. I never felt my Mind repose upon anything with complete and undistracted enjoyment — upon no person but you. When you are in the room my thoughts never fly out of window: you always concentrate my whole senses."

Research note: All primary source quotations and much of the other research in this entry can be found at a page about John Keats written and maintained by Marilee Hanson — http://englishhistory.net/